Patent GB-1332016-A (GB)
Title: Control system for use in a vehicle adaptive braking system
IPC: B60T8/70
Filed: 1971-09-02
Abstract: 1332016 Braking systems BENDIX CORP 2 Sept 1971 [10 Sept 1970] 40899/71 Heading F2F An adaptive braking system includes a pressure modulator incorporating a normally closed outlet valve with a coil 38 and a normally open inlet valve with a coil 56, energization of the coils 38, 56 being accomplished by signals received through AND gates 34, 52 and amplifiers 36, 54 respectively, which signals are measures of the rate of change of velocity of a vehicle wheel but are only transmitted through AND gates 34, 52 if a further signal from an AND gate 68 is received at AND gates 34, 52. As shown, a wheel speed sensor 10 supplies pulsed output signals to a frequency converter 12 which generates an analog signal which is then supplied to a derivative amplifier 14. The output of the derivative amplifier 14 corresponds to the rate of change of rotational velocity (acceleration or deceleration) of the vehicle wheel and this output is fed into three comparators 22, 40, 58. With reference to comparator 22, if the output of amplifier 14 exceeds a value G1 then comparator 22 will have an output which is a linear increasing voltage between wheel deceleration rates G1, G2; and as the output of comparator 22 increases from level G1 to level G2 a pulse generator 24 increases in frequency from a minimum to a maximum frequency, an inverter 30 being included in circuit. The pulsed output from the inverter 30 is fed through AND gate 34. A voltage output is generated from comparator 40 if the signal from amplifier 14 exceeds a G3 acceleration set point, this output varies linearly between G3 and G4 reference points, and this output is fed to a pulse generator 42 which pulses off at an increasing frequency. An inverter 48 delivers a signal to the AND gate 52.  The output of the amplifier 14 is also fed into a G1 reference comparator 58, which if the G1 reference point has been exceeded in a deceleration direction, then an output voltage will switch a transistor 60 to the conducting state and current flows through resistor 62, transistor 60 and charging capacitor 64. Upon receiving a predetermined amount of charge by capacitor 64 a sufficient voltage will be realised upon the input to OR gate 66 to give an output therefrom, the resistor 62, and capacitor 64 giving a charge time dependent on the value of the deceleration above G1 The output of OR gate 66 feeds to the AND gate 68 along with a voltage signal from a brake switch connected to a brake pedal. The output of the AND gate 68 is fed back into the OR gate 66 to form a latching network and is also fed to AND gates 34, 52. Thus AND gates 34, 52 will only have a voltage output if output is received from the AND gate 68 and also from their respective pulse generators; and AND gate 68 only gives an output voltage during a brake application after a predetermined period of time determined by the circuit 62, 64 and the acceleration signal applied thereto. Generator 24, its associated resistors 26, 28, 32 and inverter 30 may be excluded from the circuit so that coil 38 is energized directly from comparator 22. To compensate for changes of coefficient of friction between road surface and the vehicle wheel, an acceleration control switch 70 and one shot timer 72 may be inserted between AND gate 34 and amplifier 36, and a delay time may be utilized between outlet valve closing (de-energization) and inlet valve opening (de-energization). An acceleration responsive switch 74 may alternatively be included to alter the set point of the comparator 40. The invention is said to be applicable to full-power hydraulic systems.